Password Security Specifications: Entropy & Resistance Analysis

1.0 Threat Model Analysis

We must define the enemy. It is not a human guessing words. It is code. The primary vector for credential compromise in 2025 is the automated, offline calculation of cryptographic hashes. This is a math problem. Attackers use GPU clusters. These machines do not guess. They iterate. A single rig can test billions of combinations per second. If the search space is small, the password is gone. Additionally, "Credential Stuffing" changes the calculus entirely. If a user reuses a password, and that password leaks from a minor site, scripts will test it against banking portals immediately. A 20-character password is useless if it is public. Defense requires two things: Entropy (to stop the GPUs) and Uniqueness (to stop the stuffing).

2.0 Entropy Specifications

Strength is measured in bits. Not "complexity". The formula is E = log₂(Rᴸ).R is the pool of characters. L is length. Look at the exponent L. That is the lever. Increasing L adds massive difficulty. Increasing R (adding a symbol) adds very little. This is why "P@ssw0rd" fails. It is too short.

Compare two strings. First: "Tr0ub4dor&3". It looks hard. It has numbers, symbols, capitalization. But it is only 11 characters. And it uses predictible substitutions. A modern RTX 4090 GPU cracks this in milliseconds. Second: "correct horse battery staple". It is just words. No symbols. But it is 25 characters long. The math is unforgiving. That string has 52 bits of entropy. The same GPU would need 500 years to find it. Length wins. Every time.

3.0 Implementation Requirements

The NIST SP 800-63B guidelines are not suggestions. They are requirements for secure systems. Legacy rules are dead. Do not force rotation. When you force a user to change their password every 90 days, they do not pick a new random string. They take "Summer2024!" and change it to "Summer2025!". This is a vulnerability effectively introduced by the policy itself. Stop doing it. Also, drop the composition rules. "Must have one uppercase letter" is a roadmap for attackers. They know the first letter will be uppercase. You just reduced the search space. Enforce length. Minimum 12 characters. Ideally 16. Block common passwords. If a user tries to set "Password123", the system must reject it.

3.1 Storage Specifications

Never store plaintext. Obviously. But also: do not use fast hashes. MD5 is broken. SHA-1 is broken. SHA-256 is too fast. Speed is the enemy here. If your server can hash a password in 0.0001 seconds, so can the attacker. You need a KDF. A Key Derivation Function. These are slow on purpose.

Use Argon2id. It eats RAM. This is good. GPUs are fast at math but bad at memory access. Argon2id forces the attacker to use expensive memory for every guess. It makes cracking expensive. If you cannot use Argon2id, use Bcrypt. but crank the cost factor up. Log_rounds needs to be at least 12. Hardware is getting faster; your hashes need to get slower.

5.0 Forensic Analysis: Hashcat Benchmark Case Study

Let’s look at the numbers. A single NVIDIA RTX 4090 GPU running Hashcat v6.2.6. This is what you are fighting. MD5 algorithm: 164 billion hashes per second. At that speed, every 8-character password in existence falls in under one second. SHA-256: 22 billion hashes per second. Still too fast. Now look at Argon2id (t=2, m=64MB). Speed drops to 6,500 hashes per second. From billions to thousands. That is the difference between a breach and a nuisance. Algorithm selection is the single most critical backend decision.

Attackers are lazy. They don't brute force if they don't have to. They use "Dictionary Attacks". They take the "RockYou" list—14 million leaked passwords—and apply rules. They turn 'a' to '@'. They append '2023'. This "OneRuleToRuleThemAll" approach cracks 90% of user passwords in an hour. The only defense is randomness.

6.0 Key Derivation Function (KDF) Standards

Argon2id is the gold standard. It won the Password Hashing Competition in 2015. It resists GPU cracking (memory hardness) and side-channel attacks (data-independent access). Use it.

Bcrypt is the veteran. It is CPU-hard, not Memory-hard. It is still fine, mostly. But FPGAs are starting to hurt it. Cost factors allow it to scale, but Argon2id is technically superior.Scrypt was the first intent at memory-hardness. It works, but it has issues with side-channel attacks in multi-tenant systems. Avoid it if you have Argon2id.

7.0 Multi-Factor Authentication Standards

Passwords fail. Users get phished. You need a second factor. But not all MFA is good. TOTP (the 6 digit codes on your phone) is "okay". But it is phishable. An attacker sends a fake login link. The user types the password. The user types the code. The attacker passes both to the real site instantly. It is called a Real-Time Proxy. And it works.

The fix is FIDO2 / WebAuthn. Hardware keys. Passkeys. These use public key cryptography. The browser builds the origin (the URL) into the signature. If the user is on "fakesite.com", the key will not sign the request for "realsite.com". It kills phishing dead.

8.0 Operational Procedures

Need a master password? Use Diceware. Get physical dice. Roll them. Look up the numbers in the EFF Wordlist. "1-4-2-5-3" might be "battery". Do it 6 times. That gives you ~77 bits of entropy. The universe will end before that gets cracked.

Auditing is mandatory. Query the HaveIBeenPwned API. Check your users' emails. Check their password hashes (using k-Anonymity). If a credential is in a breach, kill it. Rotate it immediately. It is compromised.

9.0 Next-Generation Authentication: Passkeys & WebAuthn

We are moving away from "shared secrets". Passwords are shared secrets. You know it, the server knows it (hashed). Passkeys are asymmetric. The server has a public key. It is public. It can leak. It does not matter. The private key lives on your device. In the TPM. In the Secure Enclave. It never leaves. When you log in, your device signs a challenge. The server verifies the signature. No secret is ever sent over the wire. This is the endgame.

10.0 Enterprise Policy Configuration Standard

Corporate IT gets this wrong constantly. They configure Active Directory like it is 1999. A "Secure" policy looks like this (and it is bad):

{
  "password_history": 24,
  "max_age_days": 90,
  "min_length": 8,
  "complexity": {
    "require_upper": true,
    "require_special": true,
    "require_digit": true
  }
}

{
  "password_history": 0,
  "max_age_days": 0,
  "min_length": 12,
  "complexity": {
    "require_upper": false,
    "require_special": false,
    "require_digit": false
  },
  "blacklist_check": "enabled_on_creation"
}

11.0 Client-Side Security Model

The DOM is a battlefield. Browsers are helpful. Too helpful. They see <input type="password"> and they want to fill it. Javascript can see that too. Malicious scripts inject invisible forms. The browser autofills them. The script steals the data. This is "Autofill Jacking". You need explicit interaction. Require a click or a biometric prompt before filling. And XSS? If they have XSS, they have the session. HttpOnly cookies are mandatory. CSP is mandatory.

Appendix A: Technical Glossary

Brute Force Attack: Trying every key. The defense is entropy.

Credential Stuffing: Using stolen passwords on other sites. The defense is uniqueness.

Entropy (Information Theoretic): Bits of uncertainty. H = L * log2(N).

KDF (Key Derivation Function): Slow hash functions. They make the attacker work.

Salt (Cryptography): Random data added to the hash. Stops rainbow tables.

Rainbow Table: Pre-calculated hashes. Time-memory tradeoff.

Work Factor: The "Cost" dial on your KDF. Turn it up as computers get faster.

Appendix B: Adversarial Hardware Profile

It costs $18,500 to break into your system. That buys a cluster of eight NVIDIA RTX 4090s. 1,000 GH/s. One trillion passwords per second (NTLM). An 8-character password has 218 trillion combinations. This rig does that in 218 seconds. Four minutes. That is the reality.